Systems for and methods of using fold gratings for dual axis expansion

ABSTRACT

A near eye optical display includes a waveguide comprising a first surface and a second surface, an input coupler, a fold grating, and an output grating. The input coupler is configured to receive collimated light from a display source and to cause the light to travel within the waveguide via total internal reflection between the first surface and the second surface to the fold grating; the fold grating is configured to provide pupil expansion in a first direction and to direct the light to the output grating via total internal reflection between the first surface and the second surface; and the output grating is configured to provide pupil expansion in a second direction different than the first direction and to cause the light to exit the waveguide from the first surface or the second surface.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is related to and claims the benefit of U.S. patent application Ser. No. 17/718,147 filed on Apr. 11, 2022 by Stanley, et al. and entitled “SYSTEMS FOR AND METHODS OF USING FOLD GRATINGS FOR DUAL AXIS EXPANSION,” which claims the benefit of U.S. patent application Ser. No. 17/027,562 filed on Sep. 21, 2020 by Stanley, et al. and entitled “SYSTEMS FOR AND METHODS OF USING FOLD GRATINGS FOR DUAL AXIS EXPANSION,” which claims the benefit of U.S. patent application Ser. No. 14/497,280 filed on Sep. 25, 2014, all of which are assigned to the assignee of the present application and incorporated herein by reference. U.S. patent application Ser. No. 14/497,280 is related to U.S. patent application Ser. No. 14/465,763 (09KE459CC (047141-1029)) filed on Aug. 21, 2014, by Robbins et al., entitled “OPTICAL DISPLAYS,” which claims the benefit of and priority to and is a Continuation of U.S. patent application Ser. No. 13/355,360, filed on Jan. 20, 2012 (now U.S. Pat. No. 8,817,350, issued on Aug. 26, 2014) (09KE459C (047141-0834)), which claims the benefit of and priority to and is a Continuation of U.S. patent application Ser. No. 12/571,262 filed on Sep. 30, 2009 (now U.S. Pat. No. 8,233,204, issued on Jul. 31, 2012) (09KE459 (047141-0689)); U.S. patent application Ser. No. 13/869,866 (13FD325 (047141-0920)) filed on Apr. 24, 2013, by Popovich et al., entitled “HOLOGRAPHIC WIDE ANGLE DISPLAY,” which claims the benefit of and priority to U.S. Provisional Patent Application No. 61/687,436 filed on Apr. 25, 2012, and U.S. Provisional Patent Application No. 61/689,907 filed on Jun. 15, 2012, and U.S. patent application Ser. No. 13/844,456 (13FD235 (047141-0903)) filed on Mar. 15, 2013, by Brown et al., entitled “TRANSPARENT WAVEGUIDE DISPLAY PROVIDING UPPER AND LOWER FIELDS OF VIEW,” which claims the benefit of and priority to U.S. Provisional Patent Application No. 61/796,632 filed on Nov. 16, 2012, and U.S. Provisional Patent Application No. 61/849,853 filed on Feb. 4, 2013, all of which are assigned to the assignee of the present application and incorporated herein by reference.

BACKGROUND

The present disclosure relates to displays including but not limited to near eye displays. More specifically, the disclosure relates to substrate guided optics.

Substrate guided displays have been proposed which use waveguide technology with diffraction gratings to preserve eye box size while reducing lens size. U.S. Pat. No. 4,309,070 issued to St. Leger Searle and U.S. Pat. No. 4,711,512 issued to Upatnieks disclose substrate waveguide head up displays where the pupil of a collimating optical system is effectively expanded by the waveguide structure. U.S. patent application Ser. No. 13/869,866 discloses holographic wide angle displays and U.S. patent application Ser. No. 13/844,456 discloses waveguide displays having an upper and lower field of view.

SUMMARY

One exemplary embodiment of the disclosure relates to a near eye optical display. The near eye optical display includes a waveguide comprising a first surface and a second surface, an input coupler, a fold grating, and an output grating. The input coupler is configured to receive collimated light from a display source and to cause the light to travel within the waveguide via total internal reflection between the first surface and the second surface to the fold grating. The fold grating is configured to provide pupil expansion in a first direction and to direct the light to the output grating via total internal reflection between the first surface and the second surface. The output grating is configured to provide pupil expansion in a second direction different than the first direction and to cause the light to exit the waveguide from the first surface or the second surface.

Another exemplary embodiment of the disclosure relates to a method of displaying information. The method includes receiving collimated light in a waveguide having a first surface and a second surface; providing the collimated light to a fold grating via total internal reflection between the first surface and the second surface; providing pupil expansion in a first direction using the fold grating and directing the light to an output grating via total internal reflection between the first surface and the second surface; and providing pupil expansion in a second direction different than the first direction and causing the light to exit the waveguide from the first surface or the second surface.

Another exemplary embodiment of the disclosure relates to an apparatus for providing an optical display. The apparatus for providing an optical display includes a first image source for a first image for a first field of view, and a second image source for a second image for a second field of view, and a waveguide. The waveguide includes a first surface, a second surface, a first input coupler, a second input coupler, a first fold grating, a second fold grating, a first output grating, and a second output grating. The first input coupler is configured to receive the first image and to cause the first image to travel within the waveguide by total internal reflection between the first surface and the second surface to the first fold grating. The first fold grating is configured to provide pupil expansion in a first direction and to direct the first image to the first output grating via total internal reflection between the first surface and the second surface. The first output grating is configured to provide pupil expansion in a second direction different than the first direction and to cause the first image to exit the waveguide from the first surface or the second surface. The second input coupler is configured to receive the second image and to cause the second image to travel within the waveguide by total internal reflection between the first surface and the second surface to the second fold grating. The second fold grating is configured to provide pupil expansion in the first direction and to direct the second image to the second output grating via total internal reflection between the first surface and the second surface. The second output grating is configured to provide pupil expansion in the second direction different than the first direction and to cause the second image to exit the waveguide from the first surface or the second surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like elements, in which:

FIG. 1A is a planar side view schematic drawing of a dual axis expansion waveguide display system according to an exemplary embodiment;

FIG. 1B is a planar top view schematic drawing of the dual axis expansion waveguide display system illustrated in FIG. 1A according to an exemplary embodiment;

FIG. 2A is a planar top view schematic drawing of a dual axis expansion waveguide display system according to another exemplary embodiment;

FIG. 2B is a front view schematic illustration of the dual axis expansion waveguide display system illustrated in FIG. 2A according to another exemplary embodiment;

FIG. 2C is a top view schematic drawing of four output gratings forming a composite image by tiling four output images for the dual axis expansion waveguide display system illustrated in FIG. 2A according to another exemplary embodiment;

FIG. 2D is a side view schematic drawing of the dual axis expansion waveguide display system illustrated in FIG. 2A according to another exemplary embodiment;

FIG. 3A is a planar top view schematic drawing of a dual axis expansion waveguide display system according to another exemplary embodiment;

FIG. 3B is a front view schematic illustration of the dual axis expansion waveguide display system illustrated in FIG. 3A according to another exemplary embodiment; and

FIG. 3C is a top view schematic drawing of four output gratings forming a composite image by tiling four output images for the dual axis expansion waveguide display system illustrated in FIG. 3A according to another exemplary embodiment.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various concepts related to, and embodiments of, an inventive optical display and methods for displaying information. It should be implemented in any of numerous ways, as the disclosed concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.

The invention will now be further described by way of example with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be practiced with some or all of the present invention as disclosed in the following description. For the purposes of explaining the invention, well-known features of optical technology known to those skilled in the art of optical design and visual displays have been omitted or simplified in order not to obscure the basic principles of the invention. Unless otherwise stated, the term “on-axis” in relation to a ray or a beam direction refers to propagation parallel to an axis normal to the surfaces of the optical components described in relation to the invention. In the following description, the terms light, ray, beam and direction may be used interchangeably and in association with each other to indicate the direction of propagation of light energy along rectilinear trajectories. Parts of the following description will be presented using terminology commonly employed by those skilled in the art of optical design. It should also be noted that in the following description of the invention, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment.

Referring generally to the Figures, systems and methods relating to near-eye display or head up display systems are shown according to various embodiments. Holographic waveguide technology can be advantageously utilized in waveguides for helmet mounted displays or head mounted displays (HMDs) and head up displays (HUDs) for many applications, including military applications and consumer applications (e.g., augmented reality glasses, etc.). Switchable Bragg gratings (SBGs), which are holograms recorded in holographic polymer dispersed liquid crystal, may be used in waveguides to create a larger field of view with increased resolution in current display systems, including HMDs, HUDs, and other near eye displays. SBGs may also be used to increase the field of view by tiling images presented sequentially on a micro display. A larger exit pupil may be created by using fold gratings in conjunction with conventional or other gratings to provide pupil expansion on a single waveguide in both the horizontal and vertical directions, thereby enabling the use of a very small lens system. Using the systems and methods disclosed herein, a single optical waveguide substrate may generate a wider field of view than found in current waveguide systems. Diffraction gratings may be used to split and diffract light rays into several beams that travel in different directions, thereby dispersing the light rays.

Referring to FIG. 1 , an illustration of a dual axis (e.g., vertical and horizontal) beam expansion waveguide display system 100 is shown according to an exemplary embodiment. FIG. 1A is a planar side view schematic drawing of a dual axis expansion waveguide display system according to an exemplary embodiment. FIG. 1B is a planar top view schematic drawing of the dual axis expansion waveguide display system illustrated in FIG. 1A according to an exemplary embodiment. The waveguide display system 100 includes a substrate waveguide 101 and a light source 111. In some embodiments, the light from the light source 111 is polarized.

Substrate waveguide 101 includes a first surface 102, a second surface 104, an input coupler 110, a fold grating 120, and an output grating 130. The first and second surfaces 102 and 104 define the boundaries of the waveguide substrate 101 containing the fold grating 120 and the output grating 130 and are flat, planar surfaces in some embodiments. In some embodiments, waveguide substrate 101 can be a transmissive material, such as glass or plastic suitable for optical designs. The waveguide substrate 101 can be comprised of one or more layers and coatings.

Input coupler 110 can be a prism, mirror, reflective surface or grating for injecting light from the light source 111 into the waveguide substrate 101. In some embodiments, the input coupler 110 can be a holographic grating, such as a switchable or non-switchable SBG grating. Similarly, and in some embodiments, the fold grating 120 and the output grating 130 can be holographic gratings, such as switchable or non-switchable SBGs. As used herein, the term grating may encompass a grating comprised of a set of gratings in some embodiments.

The waveguide substrate 101 may include a number of layers. For example, in some embodiments, a first layer includes the fold grating 120 while a second layer includes the output grating 130. In some embodiments, a third layer can include input coupler 110. The number of layers may then be laminated together into a single waveguide substrate 101.

In some embodiments, the waveguide substrate 101 is comprised of a number of pieces including the input coupler 110, the fold grating 120 and the output grating 130 (or portions thereof) that are laminated together to form a single substrate waveguide. The pieces may be separated by optical glue or other transparent material of refractive index matching that of the pieces.

In another embodiment, the input coupler 110, the fold grating 120 and the output grating 130 can each be recorded into the same substrate to form the waveguide substrate 101. In another embodiment, the waveguide substrate 101 may be formed via a cell making process by creating cells of the desired grating thickness and vacuum filling each cell with SBG material for each of the input coupler 110, the fold grating 120 and the output grating 130. In one embodiment, the cell is formed by positioning multiple plates of glass with gaps between the plates of glass that define the desired grating thickness for the input coupler 110, the fold grating 120 and the output grating 130. In one embodiment, one cell may be made with multiple apertures such that the separate apertures are filled with different pockets of SBG material. Any intervening spaces may then be separated by a separating material (e.g., glue, oil, etc.) to define separate areas within a single substrate waveguide 101. In one embodiment, the SBG material may be spin-coated onto a substrate and then covered by a second substrate after curing of the material.

By using the fold grating 120, the waveguide display system 100 advantageously requires fewer layers than previous systems and methods of displaying information according to some embodiments. In addition, by using fold grating 120, light can travel by total internal refection within the substrate waveguide 101 in a single rectangular prism defined by surfaces 102 and 104 while achieving dual pupil expansion.

In another embodiment, the input coupler 110, the fold grating 120 and the output grating 130 can be created by interfering two waves of light at an angle within the substrate to create a holographic wave front, thereby creating light and dark fringes that are set in the waveguide substrate 101 at a desired angle. In one embodiment, the input coupler 110, the fold grating 120, and the output grating 130 embodied as holograms can be Bragg gratings recorded in a holographic polymer dispersed liquid crystal (HPDLC) (e.g., a matrix of liquid crystal droplets), although Bragg gratings may also be recorded in other materials. Bragg gratings recorded in HPDLC are known as SBGs. In one embodiment, SBGs are recorded in a special HPDLC material, such as POLICRYPS, resulting in a matrix of pure liquid crystal Bragg planes separated by solid polymer. SBGs may also be recorded in other materials, including POLIPHEM. Similar to POLICRYPS, POLIPHEM also provides a matrix of pure liquid crystal Bragg planes separated by solid polymer, however both substances are fabricated by different processes. The SBGs can be switching or non-switching in nature. In its non-switching form, an SBG has the advantage over conventional holographic photopolymer materials of being capable of providing high refractive index modulation due to its liquid crystal component.

The light source 111 can include a number of input objective lenses 112, 113, 114 and an image source 115 and can provide collimated light to the input coupler 110. The image source 115 can be a micro-display or laser based display. In one or more embodiments, the image source is a liquid crystal display (LCD) micro display or liquid crystal on silicon (LCOS) micro display.

In some embodiments, the input objective lenses 112, 113, 114 may be many different types of lenses, including, for example, projection lenses. In some embodiments, however, the light source 111 includes a single input objective lens (e.g., input objective lens 112). The input coupler 110 is configured to receive collimated light from a display source and to cause the light to travel within the substrate waveguide 101 via total internal reflection between the first surface 102 and the second surface 104 to the fold grating 120. The input objective lenses 112, 113, 114 collimate the display image on the image source 115 and each pixel on the image source 115 is converted into a unique angular direction within the substrate waveguide 101 according to some embodiments. The input coupler 110 may be orientated directly towards or at an angle relative to the fold grating 120. For example, in one embodiment, the input coupler 110 may be set at a slight incline in relation to the fold grating 120. One advantage of tilting the input coupler 110 is that the waveguide substrate 101 may also be tilted with respect to the viewer. For example, such tilting may allow the visor of FIG. 3B to provide a peripheral vision rather than a flat faceplate. Another benefit of using dual axis expansion in an optical waveguide is that smaller input objective lenses 112, 113, 114 may be used according to some embodiments. In some embodiments, at least one of the input objective lenses 112, 113, 114 may be a diffractive lens.

In some embodiments, the fold grating 120 may be oriented in a diagonal direction. The fold grating 120 is configured to provide pupil expansion in a first direction and to direct the light to the output grating 130 via total internal reflection between the first surface 102 and the second surface 104 of the substrate waveguide 101 in some embodiments. In one embodiment, a longitudinal edge of each fold grating 120 is oblique to the axis of alignment of the input coupler 110 such that each fold grating 120 is set on a diagonal with respect to the direction of propagation of the display light. The fold grating 120 is angled such that light from the input coupler 110 is redirected to the output grating 130. In one example, the fold grating 120 is set at a forty-five degree angle (e.g., 40-50 degrees) relative to the direction that the display image is released from the input coupler 110. This feature causes the display image propagating down the fold grating 120 to be turned into the output grating 130. For example, in one embodiment, the fold grating 120 causes the image to be turned 90 degrees into the output grating 130. In this manner, a single waveguide provides dual axis pupil expansion in both the horizontal and vertical directions. In one embodiment, each of the fold grating 120 may have a partially diffractive structure. In some embodiments, each of the fold grating 120 may have a fully diffractive structure. In some embodiments, different grating configurations and technologies may be incorporated in a single substrate waveguide 101.

The output grating 130 is configured to provide pupil expansion in a second direction different than the first direction and to cause the light to exit the waveguide 100 from the first surface or the second surface. The output grating 130 receives the display image from the fold grating 120 via total internal reflection and provides pupil expansion in a second direction. In some embodiments, the output grating 130 may consist of multiple layers of substrate, thereby comprising multiple layers of output gratings. Accordingly, there is no requirement for gratings to be in one plane within the substrate waveguide 101, and gratings may be stacked on top of each other (e.g., cells of gratings stacked on top of each other). The output grating 130 can be disposed approximately perpendicular to the gratings of the input couple 110 in some embodiments. In some embodiments, the output grating is disposed approximately 5-10 degrees (e.g., approximately 7.5 degrees) from the vertical axis.

In some embodiments, a quarter wave plate 142 on the substrate waveguide 101 rotates polarization of a light ray to maintain efficient coupling with the SBGs. The quarter wave plate 142 may be coupled to or adhered to the surface 102 of substrate waveguide 101. For example, in one embodiment, the quarter wave plate 142 is a coating that is applied to substrate waveguide 101. The quarter wave plate 142 provides light wave polarization management. Such polarization management may help light rays retain alignment with the intended viewing axis by compensating for skew waves in the substrate waveguide 101. In one embodiment, the output grating 130 may be contained by glass. The quarter wave plate 142 is optional and can increase the efficiency of the optical design in some embodiments. In some embodiments, the substrate waveguide 101 does not include the quarter wave plate 142. The quarter wave plate may be provided as a multi-layer coating.

Referring to FIGS. 2A-C, illustrations of a medium field of view head mounted display system 201 are shown according to an exemplary embodiment. FIG. 2A is a planar top view schematic drawing of one embodiment of a head mounted display system 201 including a dual axis (e.g., vertical and horizontal) beam expansion waveguide 200 and light sources 210 and 211. FIG. 2B is front view schematic illustration of an embodiment of the head mounted display system 201 being worn on a helmet, and FIG. 2C is a top view schematic drawing of four output gratings forming a composite image by tiling four output images for the head mounted display system 201 according to one embodiment. In one embodiment, the resolution of the composite image is formed by the tiling of four 800 by 600 images to create a composite 1600 by 1200 image in field of view space. The micro display input image may be updated synchronously with the switching of the SBGs. In some embodiments, the head mounted display system 201 provides a 30 degree by 40 degree field of view at the output grid 221 using multiplexing techniques such as those described in the applications incorporated herein by reference.

The light sources 210 and 211 may each include a number of input objective lenses 212 and image sources 215 that can provide collimated light. The image sources 215 can be micro displays or laser based displays, among other display types. In one or more embodiments, the image sources 215 are liquid crystal display (LCD) micro displays or liquid crystal on silicon (LCOS) micro displays. In one alternative embodiment, light sources 210 and 211 can be a single light source having two images for substrate waveguide 200.

In some embodiments, the input objective lenses 212 may be many different types of lenses, including, for example, projection lenses. In some embodiments, however, the light sources 210 and 211 include a single input objective lens. Pairs of input couplers on substrate waveguide 200, similar to input coupler 110, are each configured to receive collimated light from respective display sources 210 and 211 and to cause the light to travel within the substrate waveguide 200 via total internal reflection to respective fold gratings 254, 256, 258, and 260 similar to fold grating 120. The pairs of input couplers include a first pair of input couplers 214 and 216 associated with light source 210 (FIG. 2D). A second pair similar to the first pair is provided on substrate waveguide 201. The light from each respective fold grating 254, 256, 258, and 260 travels within the substrate waveguide 200 via total internal reflection to a respective output grating 224, 226, 228, and 230 similar to output grating 130 to form a respective image. FIG. 2A depicts output grating 224, 226, 228, and 230 as non-overlapping, however, it will be appreciated that the output gratings 224, 226, 228, and 230 overlap each other in some embodiments. FIG. 2A also depicts fold gratings 254, 258 as non-overlapping and fold gratings 256, 260 as non-overlapping, however, it will be appreciated that the fold gratings 254, 258, 256, and 260 may overlap in some embodiments. For example, in one embodiment, fold grating 254 and fold grating 258 overlap each other.

As shown in FIG. 2A, the substrate waveguide 200 may include the same or similar elements of the substrate waveguide 101 shown and described in relation to FIG. 1A, including fold gratings 254, 256, 258, and 260, and output gratings 224, 226, 228, and 230. In some embodiments, the head mounted display system 201 includes the light source 210 and the light source 211. Additional light sources can be utilized in some embodiments. As explained in further detail below, a light source 210 causes an image to travel from image source 215 to an input grating 214 or 216, which causes the image to travel within the substrate waveguide 200 via total internal reflection to one of fold gratings 254 or 258, which in turn causes the image to travel within the substrate waveguide 200 via total internal reflection to output grating 224 or 228, respectively. Multiplexing techniques are used such that an image is displayed by one output grating and then the other output grating to form half of a composite image. The multiplexing techniques can be used to turn gratings 214 and 216 on and off in a sequential fashion. Likewise, image source 211 causes an image to travel from image source 215 to a pair of input gratings similar to gratings 214 and 216, which then causes the image to travel within the substrate waveguide 200 via total internal reflection to one of fold gratings 256 or 260, which in turn causes the image to travel within the substrate waveguide 200 via total internal reflection to output grating 226 or 230, respectively. Multiplexing techniques are used such that an image is displayed by one output grating and then the other out grating to form half of a composite image. Together, the two half composite images form a full composite image. The gratings may be switchable and can be turned on and off, thereby deflecting light or not deflecting light, to effect multiplexing operations.

Referring to FIG. 2C, a top view schematic drawing of four output gratings forming a composite image by tiling four output images for the dual axis expansion waveguide display system illustrated in FIG. 2A is shown according to an exemplary embodiment. In some embodiments, output grid 221 includes four or more output gratings 224, 226, 228, and 230, each similar to output grating 130 and each corresponding to an output image that forms a composite image. In some embodiments, the output gratings 224, 226, 228, and 230 are switchable and can be turned on and off, thereby deflecting light or not deflecting light, to effect multiplexing operations. The output gratings 224, 226, 228, and 230 eject the light from the substrate waveguide 201 to the user. In some embodiments, the output grating 224 receives light from light source 210 via fold grating 254, output grating 228 receives light from light source 210 via fold grating 258, output grating 226 receives light from light source 211 via fold grating 256, and output grating 230 receives light from light source 211 via fold grating 260. In some embodiments, each output grating forms an image 20 by 15. Accordingly, each of light sources 210 and 211 forms an image 20 by 30. When the images formed by each light source are combined, a 40 by 30 composite image is formed. In the embodiment illustrated by FIG. 2C, each output grating 224, 226, 228, and 230 forms an image that is 800 pixels by 600 pixels, and when combined form a composite image that is 1600 pixels by 1200 pixels, however it will be appreciated that different configurations are possible. Although output grid 221 is shown as a 2 by 2 grid in a dual waveguide structure, other arrangements are possible. For example, a 3 by 2 grid can be provided on a waveguide structure including three layers or substrates. A 3 by 3 grid can be achieved using a waveguide structure including three layers or substrates and three fold gratings, three input gratings, and three output gratings per layer or substrate and three light sources, and so on. By including the light source 210 and the light source 211, the substrate waveguide 200 may create a full field of view or larger field of view. The composite image may also include an origin 238 positioned in front of a pupil of an eye of a user.

Referring to FIG. 2D, a side view schematic drawing of the dual axis expansion waveguide display system 201 illustrated in FIG. 2A is shown according to another exemplary embodiment. As shown in FIG. 2D, only half the dual axis expansion waveguide display system 201 illustrated in FIG. 2A is shown. In one embodiment, the substrate waveguide 200 may include multiple layers, such as first layer 207 and second layer 209, however it will be appreciated that additional layers, or even a single layer, may be used. In one embodiment, fold grating 228 and output grating 258 are located in the same plane within first layer 207, and therefore overlap in FIG. 2D. Similarly, fold grating 254 and output grating 224 are located in the same plane within second layer 209 and therefore overlap in FIG. 2D. The light source 210 causes an image to travel from the image source 215 to input grating 214, which causes the image to travel within the substrate waveguide 200 via total internal reflection to fold grating 254 (FIG. 2A), which in turn cause the image to travel within the substrate waveguide 200 within first layer 207 via total internal reflection to output grating 228. Likewise, the light source 210 causes an image to travel from the image source 215 to input grating 216, which causes the image to travel within the substrate waveguide 200 within second layer 209 via total internal reflection to fold gratings 224 (FIG. 2A), which in turn cause the image to travel within the substrate waveguide 200 within second layer 209 via total internal reflection to output grating 224. The images from light source 211 are provided to fold gratings 256 and 260 and output gratings 226 and 230 in a similar fashion as described above with respect to light source 210. Multiplexing techniques are used such that an image is displayed by one output grating and then the other output grating to form half of a composite image. Together, the two half composite images form a full composite image. The gratings may be switchable and can be turned on and off, thereby deflecting light or not deflecting light, to effect multiplexing operations.

Referring to FIGS. 3A-C, illustrations of a medium field of view goggle display system 301 is shown according to an exemplary embodiment. FIG. 3A is a planar top view schematic drawing of one embodiment of the goggle display system 301 including a dual axis (e.g., vertical and horizontal) beam expansion waveguide 300 and light sources 310 and 311. FIG. 3B is a front view schematic illustration of an embodiment of the goggle display system 301 being worn on a helmet, and FIG. 3C is a planar top view schematic drawing of an output grid 321 for the goggle display system 301, according to one embodiment. In some embodiments, the goggle display system 301 provides a 40 degree by 30 degree field of view at the output grid 321 using multiplexing techniques such as those described in the applications incorporated herein by reference.

As shown in FIG. 3A, the substrate waveguide 300 may include the same or similar elements of the substrate waveguide 200 shown and described in relation to FIGS. 2A-C. In some embodiments, the goggle display system 301 includes the light source 310 and the light source 311. Additional light sources can be utilized in some embodiments.

The light sources 310 and 311 may each include a number of input objective lenses 312 and image sources 315 that can provide collimated light. The image sources 315 can be micro displays or laser based displays, among other display types. In one or more embodiments, the image sources 315 are liquid crystal display (LCD) micro displays or liquid crystal on silicon (LCOS) micro displays. In one alternative embodiment, light sources 310 and 311 can be a single light source having two images for substrate waveguide 300.

In some embodiments, the input objective lenses 312 may be many different types of lenses, including, for example, projection lenses. In some embodiments, however, the light sources 310 and 311 include a single input objective lens. A pair of input couplers on substrate waveguide 300, similar to input coupler 110, are each configured to receive collimated light from respective display sources 310 and 311 and to cause the light to travel within the substrate waveguide 300 via total internal reflection to a respective fold grating similar to fold grating 120. The light from each respective fold grating travels within the substrate waveguide 300 via total internal reflection to output grid 321.

In some embodiments, output grid 321 includes four or more output gratings 324, 326, 328, and 330, each similar to output grating 130. In some embodiments, the output gratings 324, 326, 328, and 330 are switchable and can be turned on and off to effect multiplexing operations. The output gratings 324, 326, 328, and 330 eject the light from the substrate waveguide 300 to the user. In some embodiments, the output gratings 324 and 326 receive light from the first fold grating in substrate waveguide 300 and light source 310, and the output gratings 328 and 330 receive light from the second fold grating in substrate waveguide 300 and light source 311.

By including the light source 310 and the light source 311, the substrate waveguide 300 may create a full field of view or larger field of view. In some embodiments, the substrate waveguide 300 creates a full field of view or larger field of view using multiplexing techniques. For example, FIG. 3C illustrates an embodiment similar to that of FIG. 2C, except that the composite images are displayed in a horizontal orientation. In some embodiments, each output grating forms an image 15 by 20. Accordingly, each of light sources 310 and 311 forms an image 30 by 20. When the images formed by each light source are combined, a 30 by 40 composite image is formed. In the embodiment illustrated by FIG. 3C, each output grating 324, 326, 328, and 330 forms an image that is 600 pixels by 800 pixels, and when combined form a composite image that is 1200 pixels by 1600 pixels, however it will be appreciated that different configurations are possible. Although output grid 321 is shown as a 2 by 2 grid in a dual waveguide structure, other arrangements are possible. For example, a 3 by 2 grid can be provided on a waveguide structure including three layers or substrates. A 3 by 3 grid can be achieved using a waveguide structure including three layers or substrates and three fold gratings, three input gratings, and three output gratings per layer or substrate and three light sources, and so on. By including the light source 310 and the light source 311, the substrate waveguide 300 may create a full field of view or larger field of view. The composite image may also include an origin positioned in front of a pupil of an eye of a user.

In some embodiments, this configuration is utilized in a head mounted display goggle as shown in FIG. 3B, for example, a sand wind and dust goggle. In some embodiments, the output waveguide SBGs are displaced so that they line up with the eye location in the goggle. In some embodiments, an origin of grid 321 is positioned in front of a pupil of the eye of the user.

The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.

Although the figures may show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure.

The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.

Although the figures may show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. 

What is claimed is:
 1. A near eye optical display, comprising: a waveguide comprising a first surface and a second surface, an input coupler, a fold grating, and an output grating, wherein the input coupler is configured to receive collimated light from a display source and to cause the light to travel within the waveguide via total internal reflection between the first surface and the second surface to the fold grating, and wherein the fold grating is configured to provide pupil expansion in a first direction and to direct the light to the output grating via total internal reflection between the first surface and the second surface, and wherein the output grating is configured to provide pupil expansion in a second direction different than the first direction and to cause the light to exit the waveguide from the first surface or the second surface.
 2. The display of claim 1, wherein the first direction is orthogonal to the second direction.
 3. The display of claim 1, wherein the first surface and the second surface are planar surfaces.
 4. The display of claim 1, further comprising: a collimating lens system for providing light from the display source to the input coupler.
 5. The display of claim 1, further comprising: a quarter wave plate on the first surface or the second surface of the waveguide.
 6. The display of claim 1, wherein the input coupler, the fold grating, and the output grating are liquid crystal-based gratings.
 7. The display of claim 1, wherein the fold grating comprises one or more of Bragg gratings or gratings recorded in holographic polymer dispersed liquid crystal.
 8. The display of claim 1, wherein the first direction is horizontal and the second direction is vertical.
 9. The display of claim 1, wherein the display provides a field of view of at least 20 by 15 degrees.
 10. A method of displaying information, the method comprising: receiving collimated light in a waveguide having a first surface and a second surface; providing the collimated light to a fold grating via total internal reflection between the first surface and the second surface, providing pupil expansion in a first direction using the fold grating and directing the light to an output grating via total internal reflection between the first surface and the second surface; and providing pupil expansion in a second direction different than the first direction and causing the light to exit the waveguide from the first surface or the second surface.
 11. The method of claim 10, wherein the fold grating and the output grating are switchable or non-switchable Bragg gratings.
 12. The method of claim 10, wherein the first surface and the second surface are planar.
 13. The method of claim 11, wherein the input coupler is a switchable or non-switchable Bragg grating.
 14. The method of claim 11, wherein the fold grating is a first set of gratings and the output grating is a second set of gratings.
 15. The apparatus of claim 1, wherein the first direction is vertical and the second direction is horizontal.
 16. An apparatus for providing an optical display, comprising: a first image source for a first image for a first field of view; a second image source for a second image for a second field of view; a waveguide comprising a first surface, a second surface, a first input coupler, a second input coupler, a first fold grating, a second fold grating, a first output grating, and a second output grating, wherein the first input coupler is configured to receive the first image and to cause the first image to travel within the waveguide by total internal reflection between the first surface and the second surface to the first fold grating, wherein the first fold grating is configured to provide pupil expansion in a first direction and to direct the first image to the first output grating via total internal reflection between the first surface and the second surface, wherein the first output grating is configured to provide pupil expansion in a second direction different than the first direction and to cause the first image to exit the waveguide from the first surface or the second surface, wherein the second input coupler is configured to receive the second image and to cause the second image to travel within the waveguide by total internal reflection between the first surface and the second surface to the second fold grating, wherein the second fold grating is configured to provide pupil expansion in the first direction and to direct the second image to the second output grating via total internal reflection between the first surface and the second surface, and wherein the second output grating is configured to provide pupil expansion in the second direction different than the first direction and to cause the second image to exit the waveguide from the first surface or the second surface.
 17. The apparatus of claim 16, wherein the first direction is orthogonal to the second direction.
 18. The apparatus of claim 16, wherein first field of view is at least 15 by 20 degrees.
 19. The apparatus of claim 16, further comprising a third output grating and a fourth output grating, the third output grating receiving a third image for the first fold grating, and the fourth output grating receiving a fourth image from the second fold grating, the first and third grating being provided by the first image source sequentially and the second and third image being provide by the second image source sequentially.
 20. The apparatus of claim 16, wherein the first and third grating are switched sequentially to appropriately output the first image and the third image from the waveguide. 